<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>扩展卡片(调整flex值+transition)</title>
  <style>
    * {
      box-sizing: border-box;
    }

    body {
      display: flex;
      align-items: center;
      justify-content: center;
      height: 100vh;
      margin: 0;
    }

    #container {
      display: flex;
      width: 90vw;
    }

    .panel {
      background-size: auto 100%;
      background-position: center;
      background-repeat: no-repeat;
      border-radius: 50px;
      color: white;
      flex: 0.5;
      cursor: pointer;
      height: 80vh;
      position: relative;
      /*给文字标题定位*/
      margin: 10px;
      transition: flex 0.7s cubic-bezier(0.05, 0.6, 0.4, 0.9);
    }

    .panel h3{
      font-size: 24px;
      opacity: 0;
      position: absolute;
      bottom: 20px;
      left: 20px;
      margin: 0;
      transform: opacity 0s ease-in 0s;
    }
    .panel.active{
      flex:5;
      border-radius: 50px;

    }
    .panel.active h3{
      opacity: 1;
      transform: opacity .3s ease-in .4s;
    }

    @media(max-width:500px){
      #container{
        width: 100vw;
      }
      .panel:nth-of-type(4){
        display: none;
      }
      .panel:nth-of-type(5){
        display: none;
      }

    }
  </style>
</head>

<body>
  <div id="container">
    <div class="panel active" style="background-image: url(./img/img1.jpg);">
      <h3>海阔天空</h3>
    </div>
    <div class="panel" style="background-image: url(./img/img2.jpg);">
      <h3>蓝天白云</h3>
    </div>
    <div class="panel" style="background-image: url(./img/img3.jpg);">
      <h3>山川胡海</h3>
    </div>
    <div class="panel" style="background-image: url(./img/img4.jpg);">
      <h3>星空</h3>
    </div>
    <div class="panel" style="background-image: url(./img/img5.jpg);">
      <h3>森林</h3>
    </div>
  </div>


  <script>
    const panels = document.querySelectorAll('.panel')
    function removeActivesClasses(){
      panels.forEach(panel=>{
        panel.classList.remove('active')
      })
    }
    panels.forEach(panel=>{
      panel.addEventListener('click',()=>{
        removeActivesClasses()
        panel.classList.add('active')

      })
    })


  </script>
</body>


</html>